Internal transmission thermostat

Abstract

An internal thermostat for an automatic transmission of a motor vehicle includes a thermostat housing, a rotary valve and a bimetallic, temperature sensitive element. The thermostat housing is attached to an internal flow aperture of the transmission to be controlled. The rotary valve is moveable between an open position and a closed position in response to a temperature of oil, thereby controlling oil flow through the internal flow aperture of the transmission. The bimetallic temperature-sensitive element is attached to the rotary valve and operative to control an angular position of the valve as a function of the temperature of the surrounding oil. The bimetallic, temperature-sensitive element may be shaped like a coil. Alternatively, the bimetallic, temperature-sensitive element may be shaped like a substantially linear strip.

1 . An internal thermostat for an automatic transmission of a motor vehicle, the internal thermostat comprising:
 a thermostat housing attached to an internal flow aperture of the transmission to be controlled;   a rotary valve moveable between an open position and a closed position in response to a temperature of oil, thereby controlling oil flow through the internal flow aperture of the transmission; and   a bimetallic temperature-sensitive element shaped like a coil and attached to the rotary valve, the bimetallic temperature-sensitive element operative to control an angular position of the valve as a function of the temperature of the surrounding oil.   
     
     
         2 . The internal transmission thermostat of  claim 1 , wherein the rotary valve is placed in a substantially balanced arrangement in the oil flow, so that the symmetry of the pressure loads on the valve cancels out the opposite torques induced on the valve, thereby rendering the valve non-pressure sensitive and avoiding the potential risk of the valve sticking under a high pressure situation. 
     
     
         3 . The internal transmission thermostat of  claim 1 , wherein the rotary valve is placed in a non-balanced arrangement in the oil flow, in order to maximize the valve opening and achieve a high flow through the valve. 
     
     
         4 . The internal transmission thermostat of  claim 1 , in combination with the automatic transmission. 
     
     
         5 . An internal thermostat for an automatic transmission of a motor vehicle, the internal thermostat comprising:
 a thermostat housing attached to an internal flow aperture of the transmission to be controlled;   a rotary valve moveable between an open position an a closed position in response to the temperature of oil, thereby controlling oil flow through the internal flow aperture of the transmission; and   a bimetallic temperature-sensitive element shaped like a substantially linear strip that is in contact with the rotary valve and controls an angular position of the valve as a function of the temperature of the surrounding oil.   
     
     
         6 . The internal transmission thermostat of  claim 5 , wherein the rotary valve is placed in a substantially balanced arrangement in the oil flow, so that the symmetry of the pressure loads on the valve cancels out the opposite torques induced on the valve, thereby rendering the valve non-pressure sensitive and avoiding the potential risk of the valve sticking under a high pressure situation. 
     
     
         7 . The internal transmission thermostat of  claim 5 , wherein the rotary valve is placed in a non-balanced arrangement in the oil flow, in order to maximize the valve opening and achieve a high flow through the valve. 
     
     
         8 . The internal transmission thermostat of  claim 5 , wherein the substantially linear bimetal element is bent or shaped in form of one or more convolutions in order to increase its total length and therefore increase the stroke of the valve. 
     
     
         9 . The internal transmission thermostat of  claim 5 , in combination with the automatic transmission.